1. Field of the Invention
The present invention generally relates to an apparatus for regulating the speed of a member for delivering or winding yarn as a function of the draw-off speed or the delivery speed of the yarn. In particular, the invention relates to an apparatus for regulating the speed of a winding device with a pilot roller, for textile yarns, as a function of the positive delivery speed of the yarn.
2. Description of the Prior Art
The textile industry commonly uses winding devices (winders) comprising a pilot roller which is in tangential contact with a take-up roll, the function of which is to fix the peripheral speed of rotation of the take-up roll while providing all or part of the coupling required to drive the take-up roll. In general, since the winding speed must remain constant throughout the process for forming the take-up roll, the pilot roller is driven at a constant nominal speed, for example, by means of an electric motor. However, if the yarn is delivered to the winder by a positive delivery device, it is necessary to adapt the winding speed of the take-up roll to the unwinding speed of the positive delivery device at all times. The winding speed must follow the possible fluctuations (which may or may not be accidental) in the delivery speed in order to take up, at all times, the exact amount of yarn delivered, and in order to avoid the risk of breakages, non-uniform tensions and the like.
According to British Pat. No. 1,090,865, a device for regulating the speed of a pilot roller as a function of the delivery speed of a positively delivered yarn is known. The pilot roll is driven by a motor via a friction clutch which permits slipping. The speed given to the pilot roller is greater than the delivery speed of the yarn and it is adapted and regulated as a function of the delivery speed by means of a braking device which acts, by friction, directly on the pilot roller. The braking device is governed by a pneumatic pressure system controlled by a lever detecting a loop of yarn of which the length can vary as a function of the delivery speed. It is a device which employs both mechanical means and pneumatic means and is complex.
French Pat. No. 1,497,243 discloses a device for adjusting the winding tension in a yarn by controlling the winding speed in which the take-up bobbin is axially driven via an electromagnetic clutch-and-brake assembly. The variation in the braking and driving forces is achieved by varying the excitation current in the electromagnets, using an electronic circuit, by means of a potentiometer controlled by a pivoting arm which acts as a loop sensor, the position of which arm depends on the tension in the yarn.
Simpler means are also known which function in accordance with the principle of braking by means of eddy (Foucault) currents for controlling the tension in a yarn between delivery means and a draw-off device.
Thus, according to Published Application DT-OS (German Published Specification) No. 2,139,420, in order to maintain constant tension between a delivery roll and a winding roller, the delivery roll is integral with a brake operating by means of eddy (Foucault) currents. However, this device does not permit the automatic regulation of the delivery speed to match the draw-off speed.
Russian Pat. No. 178,712, describes a device for the automatic regulation of the tension in a yarn which is drawn off by a fixed take-up roll. The yarn is delivered by a roller which is caused to rotate directly by the yarn, the yarn itself being pulled downstream. The delivery roller is integral with a braking disc operating by means of eddy (Foucault) currents. The effect of the disc can vary by pushing it to a greater or lesser extent into the gap of a fixed magnet. The variations in tension are recorded by a lever provided with a guide over which the yarn passes, the prestressed lever giving the nominal tension. The lever is mechanically connected to the device and governs its displacement in the gap of the magnet, thus varying the braking of the delivery roller. This patent describes the use of braking by means of eddy (Foucault) currents for the regulation of an unwinding tension. However, it does not relate to the regulation of the speed of positive delivery means or of winding means as a function of the draw-off speed or delivery speed of the yarn.
German Pat. No. 534,277 describes a winding device comprising a braking assembly operating by means of eddy (Foucault) currents. The effects of the eddy currents can be varied, as a function of the tension in the yarn, by means of a sensor. The breaking assembly acts on a spindle which is mounted on an idler and is rotated by a yarn which is driven by a lug coaxial with the spindle. Like the preceding patent, this patent does not apply to the regulation of the speed of a positively driven member.